From a licensing perspective, Development is purely a subscription-based license. Non-Production can be perpetual or subscription, depending on your company’s entitlements. It’s best you reach out to your Account Owner/Manager for more details.

I would like to add that from my simple technical point of view, the key is that the developer license does not allow K2 to run as a Windows service, but only as a console application, and perhaps some performance limitations. If you have K2 in some virtual machine on a workstation, the Developer license probably won't be such a problem, if it's in some datacenter and shared by multiple users/developers, K2 usually has to run in a disconnected RDP session.
Contacting the account manager for information is definitely a good option.